/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nifi.processors.standard;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;

import com.fasterxml.jackson.databind.node.ObjectNode;
import com.fluenda.parcefone.event.CEFHandlingException;
import com.fluenda.parcefone.event.CommonEvent;
import com.fluenda.parcefone.parser.CEFParser;

import com.martiansoftware.macnificent.MacAddress;

import org.apache.nifi.annotation.behavior.EventDriven;
import org.apache.nifi.annotation.behavior.InputRequirement;
import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
import org.apache.nifi.annotation.behavior.SideEffectFree;
import org.apache.nifi.annotation.behavior.SupportsBatching;
import org.apache.nifi.annotation.behavior.WritesAttribute;
import org.apache.nifi.annotation.behavior.WritesAttributes;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.SeeAlso;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.annotation.lifecycle.OnScheduled;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.ValidationContext;
import org.apache.nifi.components.ValidationResult;
import org.apache.nifi.components.Validator;
import org.apache.nifi.flowfile.FlowFile;
import org.apache.nifi.flowfile.attributes.CoreAttributes;
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.io.InputStreamCallback;
import org.apache.nifi.processor.io.OutputStreamCallback;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.stream.io.BufferedOutputStream;
import org.apache.nifi.stream.io.StreamUtils;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.text.SimpleDateFormat;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.TimeZone;

@EventDriven
@SideEffectFree
@SupportsBatching
@InputRequirement(Requirement.INPUT_REQUIRED)
@Tags({"logs", "cef", "attributes", "system", "event", "message"})
@CapabilityDescription("Parses the contents of a CEF formatted message and adds attributes to the FlowFile for " +
        "headers and extensions of the parts of the CEF message.\n" +
        "Note: This Processor expects CEF messages WITHOUT the syslog headers (i.e. starting at \"CEF:0\"")
@WritesAttributes({@WritesAttribute(attribute = "cef.header.version", description = "The version of the CEF message."),
    @WritesAttribute(attribute = "cef.header.deviceVendor", description = "The Device Vendor of the CEF message."),
    @WritesAttribute(attribute = "cef.header.deviceProduct", description = "The Device Product of the CEF message."),
    @WritesAttribute(attribute = "cef.header.deviceVersion", description = "The Device Version of the CEF message."),
    @WritesAttribute(attribute = "cef.header.deviceEventClassId", description = "The Device Event Class ID of the CEF message."),
    @WritesAttribute(attribute = "cef.header.name", description = "The name of the CEF message."),
    @WritesAttribute(attribute = "cef.header.severity", description = "The severity of the CEF message."),
    @WritesAttribute(attribute = "cef.extension.*", description = "The key and value generated by the parsing of the message.")})
@SeeAlso({ParseSyslog.class})

public class ParseCEF extends AbstractProcessor {

    // There should be no date format other than internationally agreed formats...
    // flowfile-attributes uses Java 8 time to parse data (as Date  objects are not timezoned)
    private final static DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ");

    // for some reason Jackson doesnt seem to be able to use DateTieFormater
    // so we use a SimpleDateFormat to format within flowfile-content
    private final SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");


    // add a TZ object to be used by flowfile-attribute routine
    private String tzId = null;

    // Add serializer and mapper
    private static final ObjectMapper mapper = new ObjectMapper();

    public static final String DESTINATION_CONTENT = "flowfile-content";
    public static final String DESTINATION_ATTRIBUTES = "flowfile-attribute";
    public static final PropertyDescriptor FIELDS_DESTINATION = new PropertyDescriptor.Builder()
        .name("FIELDS_DESTINATION")
        .displayName("Parsed fields destination")
        .description(
                "Indicates whether the results of the CEF parser are written " +
                "to the FlowFile content or a FlowFile attribute; if using " + DESTINATION_ATTRIBUTES +
                "attribute, fields will be populated as attributes. " +
                "If set to " + DESTINATION_CONTENT + ", the CEF extension field will be converted into " +
                "a flat JSON object.")
        .required(true)
        .allowableValues(DESTINATION_CONTENT, DESTINATION_ATTRIBUTES)
        .defaultValue(DESTINATION_CONTENT)
        .build();

    public static final PropertyDescriptor APPEND_RAW_MESSAGE_TO_JSON = new PropertyDescriptor.Builder()
            .name("APPEND_RAW_MESSAGE_TO_JSON")
            .displayName("Append raw message to JSON")
            .description("When using flowfile-content (i.e. JSON output), add the original CEF message to " +
                    "the resulting JSON object. The original message is added as a string to _raw.")
            .addValidator(StandardValidators.BOOLEAN_VALIDATOR)
            .required(true)
            .defaultValue("true")
            .build();

    public static final String UTC = "UTC";
    public static final String LOCAL_TZ = "Local Timezone (system Default)";
    public static final PropertyDescriptor TIME_REPRESENTATION = new PropertyDescriptor.Builder()
        .name("TIME_REPRESENTATION")
        .displayName("Timezone")
        .description("Timezone to be used when representing date fields. UTC will convert all " +
                "dates to UTC, while Local Timezone will convert them to the timezone used by NiFi.")
        .allowableValues(UTC, LOCAL_TZ)
        .required(true)
        .defaultValue(LOCAL_TZ)
        .build();

    public static final PropertyDescriptor DATETIME_REPRESENTATION = new PropertyDescriptor.Builder()
        .name("DATETIME_REPRESENTATION")
        .displayName("DateTime Locale")
        .description("The IETF BCP 47 representation of the Locale to be used when parsing date " +
                "fields with long or short month names (e.g. may <en-US> vs. mai. <fr-FR>. The default" +
                "value is generally safe. Only change if having issues parsing CEF messages")
        .required(true)
        .addValidator(new ValidateLocale())
        .defaultValue("en-US")
        .build();

    static final Relationship REL_FAILURE = new Relationship.Builder()
        .name("failure")
        .description("Any FlowFile that could not be parsed as a CEF message will be transferred to this Relationship without any attributes being added")
        .build();
    static final Relationship REL_SUCCESS = new Relationship.Builder()
        .name("success")
        .description("Any FlowFile that is successfully parsed as a CEF message will be transferred to this Relationship.")
        .build();

    @Override
    public List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        final List<PropertyDescriptor>properties = new ArrayList<>();
        properties.add(FIELDS_DESTINATION);
        properties.add(APPEND_RAW_MESSAGE_TO_JSON);
        properties.add(TIME_REPRESENTATION);
        properties.add(DATETIME_REPRESENTATION);
        return properties;
    }

    @Override
    public Set<Relationship> getRelationships() {
        final Set<Relationship> relationships = new HashSet<>();
        relationships.add(REL_FAILURE);
        relationships.add(REL_SUCCESS);
        return relationships;
    }

    @OnScheduled
    public void OnScheduled(final ProcessContext context) {

        // Configure jackson mapper before spawning onTriggers
        final SimpleModule module = new SimpleModule()
                                        .addSerializer(MacAddress.class, new MacAddressToStringSerializer());
        this.mapper.registerModule(module);
        this.mapper.setDateFormat(this.simpleDateFormat);

        switch (context.getProperty(TIME_REPRESENTATION).getValue()) {
            case LOCAL_TZ:
                // set the mapper TZ to local TZ
                this.mapper.setTimeZone(TimeZone.getDefault());
                tzId = TimeZone.getDefault().getID();
                break;
            case UTC:
                // set the mapper TZ to local TZ
                this.mapper.setTimeZone(TimeZone.getTimeZone(UTC));
                tzId = UTC;
                break;
        }

    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {
        FlowFile flowFile = session.get();
        if (flowFile == null) {
            return;
        }

        final CEFParser parser = new CEFParser();
        final byte[] buffer = new byte[(int) flowFile.getSize()];
        session.read(flowFile, new InputStreamCallback() {
            @Override
            public void process(final InputStream in) throws IOException {
                StreamUtils.fillBuffer(in, buffer);
            }
        });

        CommonEvent event;

        try {
            // parcefoneLocale defaults to en_US, so this should not fail. But we force failure in case the custom
            // validator failed to identify an invalid Locale
            final Locale parcefoneLocale = Locale.forLanguageTag(context.getProperty(DATETIME_REPRESENTATION).getValue());
            event = parser.parse(buffer, true, parcefoneLocale);

        } catch (Exception e) {
            // This should never trigger but adding in here as a fencing mechanism to
            // address possible ParCEFone bugs.
            getLogger().error("Parser returned unexpected Exception {} while processing {}; routing to failure", new Object[] {e, flowFile});
            session.transfer(flowFile, REL_FAILURE);
            return;
        }


        // ParCEFone returns null every time it cannot parse an
        // event, so we test
        if (event==null) {
            getLogger().error("Failed to parse {} as a CEF message: it does not conform to the CEF standard; routing to failure", new Object[] {flowFile});
            session.transfer(flowFile, REL_FAILURE);
            return;
        }


        try {
            final String destination = context.getProperty(FIELDS_DESTINATION).getValue();

            switch (destination) {
                case DESTINATION_ATTRIBUTES:

                    final Map<String, String> attributes = new HashMap<>();

                    // Process KVs of the Header field
                    for (Map.Entry<String, Object> entry : event.getHeader().entrySet()) {
                        attributes.put("cef.header."+entry.getKey(), prettyResult(entry.getValue(), tzId));
                    }

                    // Process KVs composing the Extension field
                    for (Map.Entry<String, Object> entry : event.getExtension(true).entrySet()) {
                    attributes.put("cef.extension." + entry.getKey(), prettyResult(entry.getValue(), tzId));

                    flowFile = session.putAllAttributes(flowFile, attributes);
                    }
                    break;

                case DESTINATION_CONTENT:

                    ObjectNode results = mapper.createObjectNode();

                    // Add two JSON objects containing one CEF field each
                    results.set("header", mapper.valueToTree(event.getHeader()));
                    results.set("extension", mapper.valueToTree(event.getExtension(true)));

                    // Add the original content to original CEF content
                    // to the resulting JSON
                    if (context.getProperty(APPEND_RAW_MESSAGE_TO_JSON).asBoolean()) {
                        results.set("_raw", mapper.valueToTree(new String(buffer)));
                    }

                    flowFile = session.write(flowFile, new OutputStreamCallback() {
                        @Override
                        public void process(OutputStream out) throws IOException {
                            try (OutputStream outputStream = new BufferedOutputStream(out)) {
                                outputStream.write(mapper.writeValueAsBytes(results));
                            }
                        }
                    });

                    // Adjust the FlowFile mime.type attribute
                    flowFile = session.putAttribute(flowFile, CoreAttributes.MIME_TYPE.key(), "application/json");

                    // Update the provenance for good measure
                    session.getProvenanceReporter().modifyContent(flowFile, "Replaced content with parsed CEF fields and values");
                    break;
            }

            // whatever the parsing stratgy, ready to transfer to success and commit
            session.transfer(flowFile, REL_SUCCESS);
            session.commit();
        } catch (CEFHandlingException e) {
            // The flowfile has failed parsing & validation, routing to failure and committing
            getLogger().error("Failed to parse {} as a CEF message due to {}; routing to failure", new Object[] {flowFile, e});
            session.transfer(flowFile, REL_FAILURE);
            session.commit();
            return;
        } finally {
            session.rollback();
        }
    }

    private String prettyResult(Object entryValue, String tzID) {

        if (entryValue instanceof InetAddress ) {
            return ((InetAddress) entryValue).getHostAddress();
        } else if (entryValue instanceof Date) {
            ZonedDateTime zdt = ZonedDateTime.from(((Date) entryValue).toInstant().atZone(ZoneId.of(tzID)));
            return(String.valueOf(zdt.format(dateTimeFormatter)));
        } else {
            return String.valueOf(entryValue);
        }
    }


    // Serialize MacAddress as plain string
    private class MacAddressToStringSerializer extends JsonSerializer<MacAddress> {

        @Override
        public void serialize(MacAddress macAddress,
                              JsonGenerator jsonGenerator,
                              SerializerProvider serializerProvider)
                throws IOException, JsonProcessingException {
            jsonGenerator.writeObject(macAddress.toString());
        }
    }


    protected static class ValidateLocale implements Validator {
        @Override
        public ValidationResult validate(String subject, String input, ValidationContext context) {
            if (null == input || input.isEmpty()) {
                return new ValidationResult.Builder().subject(subject).input(input).valid(false)
                        .explanation(subject + " cannot be empty").build();
            }
            final Locale testLocale = Locale.forLanguageTag(input);
            final Locale[] availableLocales = Locale.getAvailableLocales();

            // Check if the provided Locale is valid by checking against the first value of the array (i.e. "null" locale)
            if (availableLocales[0].equals(testLocale)) {
                // Locale matches the "null" locale so it is treated as invalid
                return new ValidationResult.Builder().subject(subject).input(input).valid(false)
                        .explanation(input + " is not a valid locale format.").build();
            } else {
                return new ValidationResult.Builder().subject(subject).input(input).valid(true).build();

            }

        }
    }
}
